Tach signal at ECU?

[oe_tuner]

I am wiring up my Zeitronix Wideband this week. I think I have all my wiring figured out except for the tach signal. The Zeitronix instructions say I need a 12V square wave, Tach Signal or Primary side of coil signal. The Wiring diagrams I have found for the 95 claim that Pin 2I should have a Black/White wire for the Tach signal.
My ECU coupler has no Wire at all at 2I.
Does anyone have any idea where I can pick up a tach signal at the ECU for the 95 model?
Can I use one of the CAS wires that run to the ECU? Anyone know which one?
I am putting the Zeitronix unit near the ECU, so I am hoping to pull an RPM signal from the ECU rather than running a wire all the way from the meter or coil.


Thanks!

[99mx5]

Remember, to always have the wideband sensor powered up when you use the car or you will damage the sensor.

[BlownMX5]

On my '94, the tach signal was at 1H. Should be the same on a '95.

Pat.

[Tom @ Fast Forward]

My book for the 95 shows the tach signal as a black/white wire on 2I. Shows the same for the 94. 1H is a brown wire that appears to be the trigger signal to the ignition transformer. Probably would work too but might be half the number of pulses as the trigger only occurs every other time.

[BlownMX5]

Here (http://www.flyinmiata.com/support/instructions/misc/revlight.pdf) are the instructions for a shift light from FM that shows the tach signal pin on page 2. In those instructions, it shows 1H for a '94-'97, but it also shows the wire as being black w/white stripe, not brown. I also have a jpg that Chuck sent me showing the '94 ECU plug and it has 1H as being brown. I don't have my car here at work or I'd go look. I did write it on a piece of paper when I was hooking up my Zt-2 that I looked at last night when I posted. I'm pretty sure I'm using 1H and getting a good tach signal. It'll either work or it won't ;).

Pat.

[Tom @ Fast Forward]

I'm sure FM knows their business and I am not trying to fault them in any way but here is the page from the Miata manual. As you can see, there is a wire that Mazda calls TACH and it goes to 2I and it is Black with a white tracer. The wire on 1H is Brown and goes to the igniter for the coil for plugs 2 and 3. This schematic is identical for the 94-95.


http://www.fastforwardsuperchargers.com/94-95TachSignal.jpg

[oe_tuner]

Well, I found something very interesting.
I checked every wire color in the 2 ECU connectors against Tom's ECU diagram found in the Instructions section as well as against the Mitchell Wiring diagram that Tom references above (same as the one I have been using). Everything matched up except for 2 things.
My Coupler #2, Pin 2I that is supposed to have the black/white Tach wire is empty.
Also, on Coupler #1 Pin 1F which is supposed to be blank has the Black/White wire.
It seems that the only Black/White wire called out at the ECU is the signal that feeds the Tach. Do you guys think this is a reasonable assumption?
On a side note, I will have to look more into what the Zeitronix wants for RPM. I tend to agree with Tom that the coil trigger wire at 1G or 1H will only give me 1/2 of the RPM.
If any of you with 94/95's get a chance, could you take a look at your ECU and couplers, I would love to know if you have the same condition as me.
Here are some pictures of my couplers and my ECU tag.
ECU
http://new.photos.yahoo.com/oe_tuner/album/576460762388283646/photo/294928804325798365/13
Coupler 1 Bottom (Bonus 1F B/W Wire)
http://new.photos.yahoo.com/oe_tuner/album/576460762388283646/photo/294928804325807508/14
Coupler 1 Top
http://new.photos.yahoo.com/oe_tuner/album/576460762388283646/photo/294928804325798408/15
Coupler 2 Bottom
http://new.photos.yahoo.com/oe_tuner/album/576460762388283646/photo/294928804325807542/16
Coupler 2 Top (Missing 2I B/W Wire)
http://new.photos.yahoo.com/oe_tuner/album/576460762388283646/photo/294928804325798444/17
Thanks!

[Tom @ Fast Forward]

Well, I went searching and found the JRSC instructions, the ELF instructions, the JRPC instructions are all the same as mine.I also looked it up in a hardbound Miata factory manual and it also has them the same as the others. Guess FM was the only one to get it right?

[J_Man]

If any of you with 94/95's get a chance, could you take a look at your ECU and couplers, I would love to know if you have the same condition as me.

They don't have the same condition. You don't have a '94 nor '95 Miata. Yours is a '95.5 - it is a different animal (unlike the '94/'95 where the coil packs generate the tach signal, here the ECU takes care of it), etc. ... I am too tired now to write more, but just grab a multimeter or scope and it is easy to figure it out.

[J_Man]

P.S. There is a tach wire going from the ECU to the oem tach at a different ECU pin. Unlike the '94 and '95 cars it doesn't go to the coil packs. The coil packs are also different than the '94 & '95 ones

[J_Man]

I also looked it up in a hardbound Miata factory manual and it also has them the same as the others.

You won't find it there (in the '95 factory manual). The '95.5 cars (like his) are different than the '95 ones

[oe_tuner]

Thanks to everyone for your inout.

I got the Zeitronix all hooked up and it seems to be working.
I used the Black/White wire from 1F and the zeitronics is logging RPM correctly.
Now all I need is some good weather, so I can go for a run and see if the Coldside is working correctly with the new 5th injector.
Thanks again.